Method and system for changing image density and contrast

Abstract

At least one of two enhancement methods for changing contrast and/or density are applied to an image. According to a first enhancement method the window width/level settings of the image are modified and according to a second enhancement method density and contrast of the image are modified by modifying a multi-scale representation of the image whereby modification is derived from at least two gradient functions determined at different scales, a gradient function at a specific scale specifying the dependency of contrast amplification at said scale as a function of density. The amount of modification obtained by applying either of said first and second enhancement methods is determined by the amount of movement of at least one indicium.

What is claimed is: 
     
       1. Method of modifying at least one of density and contrast of an image by applying at least one of a first enhancement method for changing density and contrast by modifying the window width/level settings of said image and a second enhancement method for changing density and contrast by modifying a multi-scale representation of an image, wherein modification is derived from at least two gradient functions determined at different scales, a gradient function at a specific scale specifying the dependency of contrast amplification at said scale as a function of density, and wherein the amount of modification obtained by applying either of said first and second enhancement methods is determined by the movement of a single indicium, and wherein movement of said indicium within a predefined area determines the modification obtained by applying said second enhancement method and wherein the movement of the indicium outside said area determines the modification obtained by applying said first enhancement method. 
     
     
       2. Method according to  claim 1  wherein at least one of a first and second indicium is displayed on a display device. 
     
     
       3. Method according to  claim 1  wherein said amount of modification obtained by applying said first and said second enhancement method to said image is determined by the amount of movement of a first and second indicium respectively. 
     
     
       4. Method according to  claim 3  wherein one of said first and second indicium is a movable cursor and the other of said first and second indicium is a movable slider. 
     
     
       5. Method according to  claim 1  wherein modification resulting from said first enhancement method is established by modifying the multi-scale representation of said image, wherein modification is obtained by rescaling and translating the gradient functions along the abscissa axis. 
     
     
       6. Method of modifying at least one of density and contrast of an image by applying at least one of a first enhancement method for changing density and contrast by modifying the window width/level settings of said image and a second enhancement method for changing density and contrast by modifying a multi-scale representation of an image, wherein modification is derived from at least two gradient functions determined at different scales, a gradient function at a specific scale specifying the dependency of contrast amplification at said scale as a function of density, and wherein the amount of modification obtained by applying either of said first and second enhancement methods is determined by the movement of a single indicium and wherein the relative amount of modification by said first and second enhancement methods is determined in accordance with the deviation of the position of said single indicium from an initial reference position. 
     
     
       7. Method according to  claim 6  wherein an amount of density modification dw and the amount of contrast modification dl obtained by applying said first enhancement method and the amount of density modification dg and the amount of contrast amplification dc obtained by said second enhancement method are obtained as
     dc=x*dx  and  dw =(1 −x )* dx  with  x =tan  h ( c*dx ) and  c  a scaling factor, 
     dg=y*dy  and  dl =(1 −y )* dy  with  y =tan  h ( c*dy ) and  c  a scaling factor. 
 
     
     
       8. Method according to  claim 6  wherein the adjustments by the second enhancement method are applied until a maximum amount of contrast maxDc and density change maxDg by the second enhancement method is reached and the first enhancement method is used to further modify the image:
     dc =min( dx ,max Dc ) and  dw =max(0 ,dx−dc ) 
     dg =min( dy ,max Dg ) and  dl =max(0 ,dy−dg ). 
 
     
     
       9. Method of modifying at least one of density and contrast of an image by applying at least one of a first enhancement method for changing density and contrast by modifying the window width/level settings of said image and a second enhancement method for changing density and contrast by modifying a multi-scale representation of an image, wherein modification is derived from at least two gradient functions determined at different scales, a gradient function at a specific scale specifying the dependency of contrast amplification at said scale as a function of density, and wherein the amount of modification obtained by applying either of said first and second enhancement methods is determined by the movement of a single indicium and wherein the amount of density and contrast modification of each of the first and second enhancement methods are deduced from the trajectory of said indicium. 
     
     
       10. Method of modifying at least one of density and contrast of an image by applying at least one of a first enhancement method for changing density and contrast by modifying the window width/level settings of said image and a second enhancement method for changing density and contrast by modifying a multi-scale representation of an image, wherein modification is derived from at least two gradient functions determined at different scales, a gradient function at a specific scale specifying the dependency of contrast amplification at said scale as a function of density, and wherein the amount of modification obtained by applying either of said first and second enhancement methods is determined by the movement of at least one indicium, wherein
 the amount of density and contrast enhancement obtained by applying said first enhancement method is computed to approximate a target window width/level setting, 
 an adjustment vector defining the deviation of the position of a first indicium from an initial position is decomposed into a sum of a first adjustment vector along the direction from said initial position to said target position; and a second adjustment vector; said first and second adjustment vectors specifying the amount of contrast and density modification to be generated by the first and second enhancement methods respectively. 
 
     
     
       11. Method according to  claim 10  wherein said target window/level setting is derived from the distribution of the grey values of pixels of interest in said image. 
     
     
       12. Method according to  claim 11  wherein said target window/level setting is determined as l t =(p0+p1+k)/2 and w t =(p1+l−p0) with p0 being the minimum of the pixel values in said image and p1 being the maximum of said pixel values in said image, k and l being correction values. 
     
     
       13. Method according to  claim 12  modified in that p0 is the 1% percentile of the histogram of said image and p1 is the 99% percentile of the histogram of said image. 
     
     
       14. Method according to  claim 12  modified in that pixels of interesting said image are determined and said target window width/level setting is adjusted so that the grey value distribution of said pixels of interest covers the available range of densities in a display device. 
     
     
       15. Method of modifying at least one of density and contrast of an image by applying at least one of a first enhancement method for changing density and contrast by modifying the window width/level settings of said image and a second enhancement method for changing density and contrast by modifying a multi-scale representation of an image, wherein modification is derived from at least two gradient functions determined at different scales, a gradient function at a specific scale specifying the dependency of contrast amplification at said scale as a function of density, and wherein the amount of modification obtained by applying either of said first and second enhancement methods is determined by the movement of at least one indicium, wherein
 the amount of density and contrast enhancement obtained by applying said first method is computed to approximate a target window width/level setting,
 an adjustment vector defining the deviation of the position of a first indicium from an initial position is decomposed into an amount of contrast adjustment dx and an amount of density adjustment dy, 
 said amount of contrast adjustment dx is decomposed into an amount of contrast adjustment d w  to result from the first enhancement method to approximate the target window width setting w t  and an amount of contrast enhancement adjustment d c  to result from the second enhancement method with the combination of d w  and d c  being equal to dx, 
 said amount of density adjustment dy is decomposed into an amount of density adjustment d l  to result from said first enhancement method to approximate said target level setting and an amount of density adjustment d g  to result from said second enhancement method with the combination of d l  and d g  being equal to d y . 
 
 
     
     
       16. A computer program product in a non-transitory computer readable medium adapted to carry out a method of modifying at least one of density and contrast of an image by applying at least one of a first enhancement method for changing density and contrast by modifying the window width/level settings of said image and a second enhancement method for changing density and contrast by modifying a multi-scale representation of an image, wherein modification is derived from at least two gradient functions determined at different scales, a gradient function at a specific scale specifying the dependency of contrast amplification at said scale as a function of density, and wherein the amount of modification obtained by applying either of said first and second enhancement methods is determined by the movement of a single indicium, and wherein movement of said indicium within a predefined area determines the modification obtained by applying said second enhancement method and wherein the movement of the indicium outside said area determines the modification obtained by applying said first enhancement method. 
     
     
       17. A non-transitory computer readable medium comprising computer executable program code adapted to carry out method of modifying at least one of density and contrast of an image by applying at least one of a first enhancement method for changing density and contrast by modifying the window width/level settings of said image and a second enhancement method for changing density and contrast by modifying a multi-scale representation of an image, wherein modification is derived from at least two gradient functions determined at different scales, a gradient function at a specific scale specifying the dependency of contrast amplification at said scale as a function of density, and wherein the amount of modification obtained by applying either of said first and second enhancement methods is determined by the movement of a single indicium, and wherein movement of said indicium within a predefined area determines the modification obtained by applying said second enhancement method and wherein the movement of the indicium outside said area determines the modification obtained by applying said first enhancement method.